Saint-Gobain – whole house retrofit

Over a period of three months Saint-Gobain worked closely with Salford University, Leeds Beckett University and Saint-Gobain Recherche on what is believed to be the most in-depth study into whole house retrofit.

What attracted Saint-Gobain to the Energy House was the opportunity to work in a facility where climatic conditions could be maintained, varied and repeated and the results accurately monitored, providing the confidence that the results were due to our interventions with no extraneous factors obscuring performance.

Objectives

The objective of this phase of testing was to carry out a full retrofit of the building, but in a way that allowed stage by stage savings to be visible, in terms of performance changes in whole house heat loss and air permeability. This was carried out under closely controlled and observed conditions.

What we did

The approach to the project was based on a multi-comfort and fabric-first approach, key components of Saint-Gobain’s strategy. Multi-comfort is about careful teamwork, preparation, detailing and workmanship to achieve best practice and a significantly more comfortable and healthy internal living space for occupants.

A fabric-first approach determines that performance of the building fabric should be addressed before improvements to heating and renewables are considered. However, it was also necessary to understand the performance that can be achieved from a conventional whole-house retrofit – this was not about trying to achieve utopian performance levels.

Standard systems were installed and designed to achieve insulation levels required by Building Regulations. Areas that are often seen as difficult to insulate, such as loft eaves and external window reveals, were left untreated as might commonly occur in typical refurbishments providing data to understand the dynamics of thermal performance and airtightness at these junctions in controlled conditions.

The project team, led by Simon Gibson, R&D Manage, Saint-Gobain UK spent three months at the Energy House and the close collaboration between Leeds Metropolitan University, Salford University and Saint-Gobain Recherche resulted in measurements being taken by 414 sensors to compare pre- and post-installation energy performance, air leakage and comfort.

The ‘baseline’ was set at a level representative of the majority of UK housing. Instead of starting with the single-glazed windows of the Energy House, typical 1990’s double-glazing was installed – reflective of windows found in many properties that would benefit from improved glazing unit upgrades. The old loft insulation was retained and topped up to today’s standards. Finally, in order to test multiple solid wall insulation measures and to reflect the hybrid approach internal wall insulation was installed on the front elevation and external wall insulation on the side and rear elevations.

Results

Saint-Gobain and the project team were delighted to find that the heating demand of the property was reduced by 63%. Using typical gas costs this represented a saving of almost £350 per year and indicated that a small dwelling could be heated for less than £4 per week. A significant saving of 1.45 tonnes of CO2 per year was also indicated.

It was also notable that a 50% reduction in air-leakage resulted from the interventions and this in combination with the thermal improvements resulted in a more comfortable internal environment where more of the house could be used with no impact on energy costs, showing the value of a whole-house, holistic approach to retrofit.